The present invention relates to a linear rolling bearing, having a guide carriage which is of approximately u-shaped design and engages with its two limbs around a guide rail.
U.S. Pat. No. 5,590,965 A, for example, discloses a linear rolling bearing whose guide carriage, which is of u-shaped design, is placed onto a guide rail. The two limbs of the guide carriage engage around the guide rail which has an upper side and, situated opposite one another, two longitudinal sides. The two longitudinal sides are, in each case, provided with a plurality of ball grooves for balls. The two limbs of the guide carriage are likewise provided, on their sides which face one another, with ball grooves, with the ball grooves of the guide carriage and the ball grooves on the running rail forming load channels for the balls. In the load channel, the balls transmit loads between the guide rail and the guide carriage. The raceways in the known linear rolling bearing are aligned in an X-arrangement. Equivalent linear rolling bearings are known in which the raceways are arranged in an O-arrangement with one another. If a vertical force engages on the guide carriage, which pulls the guide carriage away from the guide rail, the balls of the lower load channel transmit this tensile force, with the upper quarter of the ball grooves formed on the guide rail accepting the tensile forces. The ball grooves can accordingly be referred to as a tension raceway.
If a compressive force is exerted on the guide carriage, the balls of both of the load channels transmit this compressive force.
The guide carriage is provided at its two end sides with, in each case, one scraper for scraping foreign objects such as chips, dust and cooling liquids from the guide rail. The scraper has a scraping system which can be formed by a sealing lip or a sealing edge. The scraping system is in scraping contact with the longitudinal sides and the upper side of the guide rail. For this purpose, the scraper, on its scraping system, has a contour which is matched to the guide rail, so that the scraping system also engages into the ball grooves.
When the guide carriage is mounted onto the guide rail, it is to be ensured that the scraper with its scraping system is aligned correctly with respect to the guide rail. This is necessary, in order to ensure correct scraping contact of the scraper with the guide rail. Only when the scraper is positioned correctly can it be fixed to the guide carriage.
If the scraping system is formed by a sealing lip, the sealing lip bears, with slight elastic preload, both against the upper side and also against the two longitudinal sides of the guide rail. If consideration is given to that part of the sealing lip which bears against both longitudinal sides of the guide rail without considering that part of the sealing lip which bears against the upper side of the guide rail, the elastic restoring forces of the sealing lip which bears against both sides of the guide rail are in force equilibrium. It is possible that correct positioning of the scraper is given on account of the force equilibrium. In reality, however, the elastic restoring forces of that part of the sealing lip which is pressed against the upper side of the guide rail are also active. The restoring force of the sealing lip which is active here pulls the scraper upward, so that those parts of the sealing lip which are pressed against the longitudinal sides of the guide rail are likewise pulled upward. This means, however, that those parts of the sealing lip which engage into the tension raceway of the guide rail are impermissibly pushed together. A correct action of the scraper is therefore not ensured. If the scraper is fixed to the guide carriage in this incorrect position, this results at least in considerably increased wear of the sealing lips in the region of the tension raceway.
The problem can also occur in the case of linear rolling bearings which are mounted in only one plane.